1. Field of the Invention
The present invention relates to a charging and discharging control circuit that controls the charging and discharging operation of a secondary battery and a charging type power supply device for the secondary battery which includes the charging and discharging control circuit therein.
2. Description of the Related Art
As a conventional charging type power supply device for a secondary battery, there has been known a power supply device shown in a circuit block diagram of FIG. 5. For example, Japanese Patent Application Laid-opn No. Hei 4-75430 xe2x80x9ccharging type power supply devicexe2x80x9d discloses the structure of the above power supply device. That is, an external terminal xe2x88x92V0 or +V0 is connected with a secondary battery 101 through a switching circuit 102. Also, a charging and discharging control circuit 110 is connected in parallel with the secondary battery 101. The charging and discharging control circuit 110 has a function of detecting a voltage across the secondary battery 101. In the case where the secondary battery is in an over-charge state (a state where the battery is higher than a given voltage value, hereinafter referred to as xe2x80x9cover-charge protective statexe2x80x9d) or an over-discharge state (a state where the battery is lower than the given voltage value, hereinafter referred to as xe2x80x9cover-discharge protective statexe2x80x9d), a signal is outputted from the charging and discharging control circuit 110 so that the switching circuit 102 turns off. Also, when the external terminal +VO reaches a certain voltage, the switching circuit 102 turns off, and the discharging operation stops, thereby being capable of limiting a current that flows in the switching circuit 102.
In other words, the discharging operation can stop (over-current control) when an excessive current flows in the switching circuit 102. Hereinafter, this state is called xe2x80x9cover-current protective statexe2x80x9d. The charging and discharging control circuit serves to protect the battery from those states.
For example, the following structure is generally applied. That is, in the case of controlling the charging and discharging operation of a lithium ion battery, in order to protect the lithium ion battery from being over-charged, when it is detected that a terminal voltage is equal to or higher than a given level, the switching element of the switching circuit turns off after a given period of time given by a delay circuit to inhibit the charging operation.
As a result, the over-charge state is positively detected without responding to a transitional change in a battery voltage, and the operation of charging the secondary battery is controlled so that the secondary battery is not brought into the over-charge state. In addition, in the charging and discharging control circuit, a control for stopping to supply a current from the secondary battery to a load while the over-discharge is detected and a control for stopping to supply a current from the secondary battery to the load while an over-current from the secondary battery to the load is detected are conducted likewise. In those controls, a delay circuit is used for each of those controls for the same reason. For example, in the case of controlling the charging and discharging operation of the lithium ion battery, a delay time of several hundreds mS to several S is required.
However, in case of the charging and discharging control circuit including the delay circuit therein, there is a case in which a terminal that enables the delay time to be changed from the external cannot be prepared due to the limit of the number of terminals of the circuit. In this case, when the over-charge detection voltage and the over-discharge detection voltage are examined, an output signal is not outputted until time periods, which are equal to or longer than the respective delay times, elapse in the respective examinations. In order to recognize the output signal, the time periods, which are equal to or longer than the respective delay times, need to elapse, with the result that the examination period of time of the charging and discharging control circuit is elongated, and the circuit manufacturing costs may be increased.
The present invention has been made to solve the above problem inherent in the prior art, and therefore an object of the present invention is to enable a period of time of examination to be reduced and the manufacturing costs to reduce by entering a test mode of shortening a delay time of an internal control circuit in the case where a voltage equal to or higher than a regulated value is applied to a charger connection terminal of a charging type power supply device.
In order to achieve the above object, according to the present invention, there is provided a charging and discharging control circuit, comprising: over-charge voltage detecting means, over-discharge voltage detecting means or over-current voltage detecting means for a secondary battery; an internal control circuit which inputs and processes signals from said over-charge voltage detecting means, said over-discharge voltage detecting means or said over-current voltage detecting means and outputs a signal for controlling the charging and discharging operation; and a delay circuit that inputs the output of said control signal and outputs a signal after a constant delay time; wherein a delay time of said delay circuit is shortened when a voltage equal to or higher than a regulated voltage is applied to the charging connection terminal.
Also, according to the present invention, there is provided charging and discharging control device, comprising: a secondary battery connected to an external power supply terminal through a switching circuit; and a charging and discharging control circuit including over-charge voltage detecting means, over-discharge voltage detecting means or an over-current detecting circuit, an internal control circuit, a delay circuit and a current control switching circuit for controlling said switching circuit; wherein a delay time of said delay circuit is shortened when a voltage equal to or higher than a regulated voltage is applied to the charging connection terminal.